The invention concerns a method for inspecting pipelines, in particular for detecting material faults in pipelines using ultrasound, wherein measuring sensors transmit ultrasound signals during passage through a pipeline, and signals reflected on boundary regions, such as surfaces or defects of a pipe wall are measured and evaluated. The invention also concerns a device for inspecting pipelines, in particular as part of a device which is passed through a pipeline, with at least one sensor support having measuring sensors which are arranged substantially circularly around the sensor support.
Laid pipelines require regular automized damage-free inspection for corrosion, pitting or the like. These defects can be determined by observation of associated pipe wall thickness variations and by their physical properties.
With appropriate radiation into the pipeline wall, the travel time differences between signals reflected on an inner wall and an outer wall as well as on defect locations in the pipeline are measured, the measurement results are tagged with a pipe section information, and are optionally intermediately stored for assessment after carrying out the test run and/or evaluated online. A device of this type is thereby usually connected to a component of the device for passing through the pipeline which has at least one pressure-tight housing for receiving means for processing and recording the measured value and for the supply of power.
EP 0 271 670 B2 discloses a method for detecting corrosion or the like on pipelines, wherein a device for inspecting the pipe walls is passed through a pipeline using a device for passing through a pipeline (pig) and transmits ultrasound signals whose travel time differences between reflection on the inner wall and outer wall of the pipeline is measured. The difference between these travel times determines the thickness of the pipe wall. Disadvantageously, small pittings are difficult to detect.
EP 0 255 619 B1 discloses a device to be moved through a pipeline for inspecting same which is provided with a circular support for ultrasound measuring heads transmitting ultrasound signals, which are disposed about the circumference of the support at regular intervals and having sensor surfaces which are always perpendicular to the normal to the pipe wall.
Disadvantageously, the above-described prior art method or device only detects corrosion and pitting, however not cracks. For detecting cracks extending up to the surface of a pipe, radiation must be applied at an angle and an additional run is required with a pig having sensors of different orientation. This only permits detection of cracks extending up to the surface of the pipe wall but not of cracks inside the wall.
It is therefore the underlying purpose of the present invention to produce a method and a device for inspecting pipelines, the device being of simple construction and reliably also detecting cracks in addition to surface corrosion and pitting, in particular cracks inside of the pipe wall and in a single measuring passage.